The hydration of olefins utilizing as catalysts sulfuric and sulfonic acids is known in the art, see for example British patent specification No. 1,518,461 issued July 19, 1978. The use of the conventional sulfuric acid and sulfonic acid catalysts have the drawback that certain by-products such as sulfates and ketones are produced. The use of the alpha-hydroxysulfonic acids of the instant invention minimizes these by-products as well as provides a more active catalyst.